The present invention relates to a method for synthesizing 2-fluoro-2-deoxy-D-glucose with an [.sup.18 F]fluoride ion prepared without addition of a carrier to produce a radiopharmaceutical for Positron Emission Tomography (PET). More particularly, the present invention relates to a method for making 2-[;8F]fluoro-2-deoxy-D-glucose involving the replacement of the trifluoromethanesulfonyl group (triflate) with an [.sup.18 F]fluoride ion, in 1,3,4,6-tetra-O-acetyl-2-triflate-.beta.-D-mannopyranose, where a phase-transfer catalyst is used in the form of a tetraalkylammonium bicarbonate, or a mixture of a tetraalkylammonium hydroxide and an alkali bicarbonate. Prior to the present invention, various procedures were used for making 2-[.sup.18 F]fluoro-2-deoxy-D-glucose or "[.sup.18 F]2FDG", which is the most widely used radiopharmaceutical ositron Emission Tomography (PET). Considerable effort has been expended in the development and refinement of such procedures. Because of its decay energy, (0.64 MEV) the [.sup.18 F]fluoride ion allows the highest inherent resolution during PET measurements and has a relatively convenient half life of 109.7 min. The following equation illustrates the preferred procedure for making [.sup.18 F]2FDG: ##STR1## where Ac is acetate, and PTR is phase-transfer reagent.
One methOd of synthesizing [.sup.18 F]2FDG by the above procedure is shown by Hamacher et al., Journal of Nuclear Medicine, 27:235-238, (1986). Hamacher et al. employ an aminopolyether [Kryptofix 222 or K222]-potassium carbonate complex as a phase-transfer catalyst for [.sup.18 F]fluoride. An additional procedure for making [.sup.18 F]2FDG is shown by Brodack et al., Applied Radiation and Isotope, Volume 39, No. 7, pages 699-703 (1988) involving the employment of a tetrabutylammonium hydroxide as a phase-transfer catalyst in place of the aminopolyether potassium complex of Hamacher et al. Although Brodack et al. disclose that the triflate reacts with [.sup.18 F]fluoride ion using the tetrabutylammonium counter ion, a yield of 12-17% is reported which is significantly below the level considered acceptable for commercial robotic production of [.sup.18 F]2FDG.